In the creation of a lens surface using surfacing generating systems, such as disclosed in U.S. Pat. No. 4,989,316 issued to Logan et al., data describing prescription information is transmitted to the surface generating system, and is thereafter used by the machine to cut the interiorly disposed surface of the lens to create the desired lens. Automatic lens blocking machines presently in the marketplace, such as disclosed in U.S. Pat. No. 5,505,654 issued to Wood et al., bond the finished outer surface of the lens blank to a block for holding the lens so that it can be placed in the surfacing machine during a cutting operation and in a lapping machine during the fining and polishing process. In these machines, the lens blank is precisely positioned in a blocking station where a block is bonded to the lens blank.
Generally, the lens blank outer surface and the block must be bonded in precise alignment with one another in accordance with prescription data and manufacturing parameters because the surface generator machines the inner surface with reference to the block, and the correct prescription can be achieved only if the inner surface of the lens blank is aligned correctly with the outer confronting surface of the block. This relative positioning of the block and the lens blank opposing surfaces affects the accuracy of obtaining a desired lens thickness, since this outcome is dependent on the spacing of the block and the outer surface of the lens blank. Also, prismatic power depends on centering and skewing of the block on the outer surface of the lens blank. Cylinder power axis, required for astigmatism correction, depends on angular orientation of the block relative to any rotationally asymmetrical elements on the outer surface of the lens blank. Thus, a number of factors influence the relative positioning of the lens blank relative to the block. However, once the block is bonded to the lens blank, it is difficult to ascertain information about the specific lens blank, such as measurements that may be useful for ultimate surface generation of the lens blank, such as the center point of the lens blank or any tilt of the lens blank with respect to the block.
In existing blocking machines in the marketplace, sensors are provided for alerting the user if a lens blank or a block is not detected at the blocking station before blocking is initiated. Additionally, sensors are provided to automatically start and stop the flow of bonding material so as to eliminate material overflow in the blocking station. Further, existing machines have used sensors positioned within the center of a block reservoir of a blocking station to detect the presence of the lens blank and the depth of the lens blank when pressed down thereby. However, these existing machines and sensors do not provide adequate information about the lens blank, such as sag and tilt, which information is difficult to ascertain once the block is bonded to the lens blank.
It is therefore an object of the present invention to provide an apparatus of the aforementioned type in which measurement data about a lens blank is automatically sensed and determined during the blocking process.
A further object of the present invention is to provide a blocking station having a block sensing support system which, during a bonding operation, senses data regarding the lens blank, including the existence and amount of sag and tilt thereof.